If a user tries to switch off the ‘Enable 3G switch’ in Settings during an active Facetime call on an iPhone with iOS 5.1.1, one get an error message. According to Apple Insider:
“the warning message does, in fact, display when the iPhone’s 3G is disabled during a FaceTime call. In addition, iOS also displays another message when a user attempts to turn 3G back on: “Enabling 3G will end your phone call. Are you sure you want to enable 3G?” Neither enabling or disabling 3G interrupted any FaceTime calls.”
This was first discovered by a Romanian Apple website – iDevice. Regardless of the warnings, Facetime calls can continue over Wifi, whether you switch 3G on or keep it off. But the warnings seem to indicate that Apple has plans to make Facetime available on 3G connections as well.
When introduced, Facetime had been disabled on 3G on the request of mobile carriers in the US, and should Apple go ahead with this plan, there’s a high likelihood that it will be blocked anyway. Moreover, with unlimited data plans being replaced by expensive,tiered plans instead, the viability of using Facetime over a wireless data connection remains to be seen.